This application is not referenced in any microfiche appendix.
This invention relates to a guide for use on a sucker rod for purposes of stabilizing a sucker rod as it is reciprocated in tubing and/or for scraping paraffin from the tubing wall.
A primary source of energy used in the world today is derived from liquid crude oil that is extracted from subterranean formations. When a well is drilled into an oil-bearing stratum, the pressure within the stratum may be sufficient to force the crude oil to the earth""s surface and in such case, no pumping action is required. However, in many areas of the world, the subterranean pressure is insufficient to force crude oil to the earth""s surface and therefore it must be pumped from the oil-bearing formation to the earth""s surface to be processed and refined. Some oil-bearing formations have sufficient formation pressure to initially force crude oil to the earth""s surface when a well is first drilled but after time the formation pressure diminishes to the point that the crude oil can be extracted only by pumping.
Crude oil can be pumped from a subterranean formation to the earth""s surface in a number of ways including electrically driven centrifugal down hole pumps, hydraulically actuated down hole pumps and hydraulically actuated jet pumps. However, a most common means of pumping oil from a subterranean formation to the earth""s surface is by means of sucker rod actuated pumps.
When the typical oil well is drilled, a casing is installed to prevent cave-in, the casing extending from the earth""s surface to the bottom of the well. To convey fluid from the formation to the surface, a string of tubing is typically run inside the casing. When a sucker rod pump is employed, it is anchored within a lower end of the tubing and the pump is reciprocated by means of a string of sucker rods extending from the earth""s surface. Sucker rods are typically formed of steel and are installed by means of couplings that are attached between threaded ends of the rods. A typical sucker rod may, for instance, be of about 25 feet in length with a coupling between each length of rod. The sucker rods reciprocate within tubing which typically may be 2-4 inches in internal diameter. Pumped oil wells vary in depth from a few hundred feet to several thousand feet. If an oil well is not perfectly vertical (and very few wells are perfectly vertical) the sucker rods tend to slide against the interior surface of the tubing. Couplings are of larger diameter than the sucker rods. Vertical reciprocation of a sucker rod couplings against the interior surface of tubing is detrimental both to the coupling and to the tubing itself. Over a long period, a coupling can wear to the point it becomes defective causing the sucker rods to separate or a hole can be worn in the tubing causing crude oil production to flow out the hole of the tubing instead of to the earth""s surface. Further, in deep wells there may be a tendency for sucker rods to whip against the interior walls of the tubing even if the tubing is substantially vertical. For all of these reasons in some wells it is important to provide stabilizers on the exterior of sucker rods to prevent excess wear of sucker rod couplings and the interior of the tubing.
Another problem encountered in pumping oil wells is paraffin. Most crude oil contains some paraffin, however, in some areas of the world the amount of paraffin in crude oil is significant. The temperature of producing formations is normally sufficiently high in that paraffin remains dissolved in the crude oilxe2x80x94that is, the paraffin remains liquid and can be pumped with the crude oil without any problem. However, as crude oil rises from a producing zone towards the earth""s surface, the temperature gradually decreases. If the crude oil has significant paraffin, the temperature of the crude oil may reduce to the point that paraffin starts to congealxe2x80x94that is, to be transformed from a liquid state to a solid state. As paraffin solidifies, it can adhere to the interior of tubing and ultimately become so thick on the tubing wall as to impair fluid flow to the earth""s surface. To combat this it has been a known practice in the petroleum industry for many years to install paraffin scrapers on sucker rods for scraping at intervals equal to or slightly less than the stroke of the pump jack to keep the walls of the tubing from closing in to the point that fluid flow is restricted.
The invention herein is intended to attack not only the problems of sucker rod wear and stabilization but also paraffin removal.
The use of sucker rod guides and/or paraffin scrapers is very well known in the petroleum industry. For background information about the construction and operation of sucker rod guides and paraffin scrapers reference may be had to U.S. Pat. No. 4,995,459 issued to John F. Mabry on Feb. 26, 1991.
For additional information about sucker rod guides and/or paraffin scrapers see the following issued U.S. Patents:
The invention herein is a sucker rod guide for use on a sucker rod that is vertically reciprocated within oil well tubing. The term xe2x80x9csucker rod guidexe2x80x9d as used herein, means a device to keep sucker rods centered within oil well tubing and that simultaneously act to scrape or dislodge paraffin from the tubing interior wall. Thus xe2x80x9csucker rod guidexe2x80x9d is inclusive of a paraffin scraper. The sucker rod guide of this invention is formed of tough, non-metallic preferably plastic material of a type that withstands elevated temperatures, and severe frictional wear, such as polyphenylene sulphide or nylon.
The sucker rod guide is formed of an elongated tubular body portion that concentrically surrounds the sucker rod. A first and second guide portion integrally extend from the body portion. Each guide portion has a semi-cylindrical guide surface of diameter slightly less than xe2x80x9cDxe2x80x9d. Each guide portion has one portion with an arc of about 180xc2x0. The second guide portion is rotationally diametrically opposed to the first guide portion so that the opposed guide surfaces together provide about 360xc2x0 of guide surface adjacent the tubing internal cylindrical surface so that thereby as the sucker rod to which the guide is affixed is reciprocated, the guide surfaces not only support the sucker rod centrally within the tubing but scrape loose accumulated paraffin from the entire cylindrical tubing wall.
The opposed guide surfaces are elevationally displaced with respect to each other to provide a pair of diametrically opposed fluid flow passageways which freely permit the flow of fluid past the sucker rod guide.
In a preferred embodiment, the guide surface on each of the guide portions is substantially in a teardrop formxe2x80x94that is, having a semi-cylindrical surface with an arc at one end that is about 180xc2x0 with the arc of the guide surface tapering to a few degrees at an opposite end. The teardrop shaped guide surfaces are reversed with respect to each other providing non-linear fluid flow passageways therebetween. In another embodiment, the guide surface of each of the guide portions is substantially of a diamond shape in configuration with pointed upper and lower ends. In still another embodiment each of the guide portions has a guide surface t hat i s semi-cylindrical with generally planar surfaces at the upper and lower ends, the planar surfaces being generally taken in planes that are at an acute angle relative to the longitudinal axis of the sucker rod to which the guide s are affixed. In all cases, irrespective of the configuration of the guide portions they are rotationally directly opposed and oppositely elevationally oriented with respect to each other to provide flow channels therebetween for the passage of fluid.
The sucker rod guide of this invention can be employed in two basic formats. In the first way they are molded directly onto a sucker rod at spaced intervals, the distance between the intervals being slightly less than the length of stroke of the pumping unit for which the sucker rods are to be employed. Molding sucker rod guides directly onto sucker rods is normally done in a factory setting.
The second basic method of using the sucker rod guide of this invention involves producing molded halves, two of which snap together to make a complete sucker rod guide. In the preferred arrangement the halves of the molded sucker rod guide are identical requiring only a single mold design for producing halves that can be joined together by a sliding slant locking action. The sucker rod guide in the form of molded halves can be installed at a location in the oil field.
The molded halves each provide two pairs of integral tangs and two pairs of tang slotsxe2x80x94that is, each side of each half of a molded sucker rod guide has a protruding tongue like tang portion and adjacent to a tang receiving recess. The tangs and recesses are shaped to provide interlocking relationships so that when one-half of a sucker rod guide is slipped into position adjacent a mating half each side of the sucker rod guide is locked to an opposing half of the sucker rod guide by the interlock relationship of tangs and tang slots. An important feature of this invention is that the tangs and tang slots by which two halves are locked into position around a sucker rod are positioned centrally of the guide opposed ends.
Each molded half of a sucker rod guide has interfitting inclined arcs that, as the halves are slid into a mating relationship with each other, provide a tightening effect to cinch the two halves together around a sucker rod as the tangs snap into the tang slots in final locked positions.
A more complete understanding of the invention will be obtained from the following description of the preferred embodiments, taken in conjunction with the attached drawings.